Lock-stitch sewing machine



May l1 1926. 1,583,926

M.HEMLEB LOCK STITCH sEwI'G MACHINE Filed March 26. 192 2 Sheets-Sheet l .lll

J3 Z0 JB J1 9 l INVENTOR a /f MM wlTNEssEsj 2 I ATTORNEY A May 1l 1926. 1,583,926

` M. HEMLEB LOCK STITCH SEWING MACHINE Fi`1ed March 26. 1924 zsheets-Sheet 2 f f f V s ai s E i @fr J ld 4 16 INVENTOR wl Nesas BY d ATTORNEY Cil Patented May 11, 1926.

UNITED STATES LSSMZ@ PATENT OFFICE.

.MARTIN HEMLEB, OF ELIZABETH, NEW JERSEY, ASSIGNOR T0 THE SINGER MANIL FACTURING COMPANY, OF ELIZABETH,

JERSEY.

NEW' JERSEY, A CORPORATION O F NEW LOCK-STITCH SEWING MACI-IIN Application filed March 26, 1924. Serial No. 701,894.

This invention relates to high-speed lockstitch sewing machines, more particularly o f the type represented in my copending application Serial No. 651,800, filed July 16, 1923, wherein a rotary hook is 'provided for carrying the needle-loop around a stationary bobbin-thread case. With stitch-forming mechanism of this type, it is necessary to provide means for restraining the thread-case against rotation while permitting free passage of the needle-loops about the threadcase. The rotation restraining means may, for example, comprise a tongue mounted on the frame of the machine and loosely7 entering a notch in the thread-case. As the needle-loop is being drawnl up, Vit is necessary for such loop to ultimately pass through the space between said tongue and thewalls of said notch, and much difficulty has 1n the past been experienced in 4securing free and easy passage of such loop through such space at high speeds. The difficulty spoken of 1s increased by yan increase in the size of the under thread-mass which necessitates the use of a larger and consequently heavier thread case, the inertia of which is a prominent factor to be reckoned With.

When sewing with certain threads, for example, wiry threads, the needle-loops have a pronounced tendency to twist and kink, particularly at the' times when such loops are being drawn up after escaping from the thread-case. This twisting or kinkirig often prevents the complete taking up of the needle-loops and such loops make an unsightly showing on the under face of the work. If the usual sewing tension is increased in an effort to accomplish the complete drawing Vup of Asuch loops, thread breakage is likely to result.

Further, in machines wherein a stationary bobbin-case is supported within the field of action of the looptaker, the Apassage ofthe needle-'thread loops about the bobbin-case necessitates the cyclical lifting of the bobbin-case from its support. Where, as in a machine such as disclosed in my said copending application, a large bobbin-case is used, and mechanical means lare vemployed for lifting the bobbin-case, there is a tendency for such case to harshly strike the raceway in the hook, causing friction and noise.

I have discovered that by providing means close to the under face of the throat-plate for yieldingly nipping and preventing twisting of the needle-thread loop until it is reduced to the smallest possible size, finally allowing the loop to escape with a snap, that is, while under a light strain or tension, like a stretched rubber band, such loop will when released. fly up to the work .so quicklyv that it has no time to twist or kink. llhatever the action may be, experiment has demonstrated that a machine equipped with this spring will satisfactorily sew at high speeds using wiry threads which cannot be as satisfactorily handled without it under equivalent coaditions of speed and under-thread capacity. I have also discovered that by opposing such spring to the bobbin-case lifting means, overthrow of the bobbin-case is prevented and a quieter and more nearly frictionless operation is secured.

In the accompanying drawings. Fig.' 1 is an elevation of the stitch-forming instrumentalties of a rotary hook sewing machine embodying the invention. Fig. 2 is a plan view of the under thread mechanism. Figs 3, 4 and 5 are views similar to Fig. 1 at successively later stages of a stitch-forming cycle, showing the passage of a needle-thread loop through the rotation restraining` notch and the control and tensioning of such loop, and Fig. 6 is a fragmentary front end elevation of the machine showing the parts above the throat-plate.

For the purposes of the present disclosure the invention is described as embodied in a rotary hook sewing machine having the constructive features represented in my said copending application. Such a machine is constructed with a reciprocating needle 1 and a rotary hook 2 making` three revolutions to one reciprocation of the needle. The machine also has the usual throat-plate 3, presser-foot 4L and feed-dog 5 which latter is carried by the feed-bar v6 and is given feedand-return movements by the shaft 7 and rising-and-falling movements by the shaft 8.

The needle 1 is carried by the needle-bar a actuated by the crank b on the shaft c through the usual link connection al. Thev needle-thread passes, as usual, through the upper thread-tension e, under the light check spring f, ,through the take-up g `and thence to the needle.

Supported within the lield of action of the rotary hook 2 on the hanger-disk 9 is the thread-case 10 having ledges 11 resting upon the hanger-disk. The thread-case is formed with the rotation restraining notch 12, Fig. 2, which is loosely entered by the tongue 13 carried by the hanger-disk 9 said tongue including a movable jaw 14 which may be eX- panded by manipulation of the latch 15, Fig. 1, to grip the adjacent wall of the notch 12 for removal of the bobbin-case. When in operative position the tongue 13, including the jaw 14.l does not fill the space between the forward and rearward walls of the notch 12 and it is through this space that the needie-loop must be drawn in its passage up to the work.

The present machine also preferably einploys a mechanical lifter 16 which is actuated by the feed-lifting rock-shaft 8 and en gages the thread-case 10 and lifts the ledges 11 clear of the hanger-disk 9, Fig. 3, as the needle-loop is being drawn up, so that the said loop is not obliged to stand the strain of bodily lifting the thread-case.

Secured to the hanger-disk 9 by screws 17, Fig. 1, are the leaf-spring 18 and its guard 19. The upper free end of the spring 18 bears lightly a ainst the rearward wall of the loop-detainmg horn 2O at the extreme upper end of the latter and normally holds open the mouth 21 of the passageway between the tongue 13 and the forward wall of the notch 12; said mouth being at that side of the tongue 13 first passed by the rotary hook and thus in position toy readily receive the supply limb of the needle-loop being drawn up. The spring 18 also overhangs one of the ledges 11, as shown in Fig. 2, and cushions the upward movement of the bobbin-case under the influence of the lifter 16, thus reducing friction and noise by preventing the nobbin-case from harshly striking the raceway in the hook 2.

The passage of the needle-loop about the bobbin-case is accomplished in substantially the same manner as described in my said copending application.' In the present instance, however, the work-limb of the needle-loop is detained by the spring 18'while the supply limb is drawn iirst into the open mouth 21 of the passageway between the tongue 13 and the walls of the notch 12. Finally, after having been drawn through said passageway, the loop is drawn between the tension-spring 18 and the horn 20 as shown in Fig. 5, and is frictionally held under control and prevented from twisting until it is reduced to the smallest possible size. The needle-thread is at this time under a light strain or tension, caused by the tensioning action of the nipper spring 18, so that when the needle-loop escapes from such spring it escapes with a snap and will be jerked up to the work before it has time to twist or kink. The action of the checkspring f, or the natural elasticity of the thread, or both, contribute to the quick take up of the needle-loop when released by thc spring 18. l

Having thus set forth the nature of thc invention, what I claim herein is 1. In a sewingmachine, a reciprocating needle, a loop-taker a bobbin-case, a rotation restraining device associated with said b0bbin-case,- a takeup, and a yielding thread-nipper through which the needle loop is drawn by thtL take-up after such loop hasl passed between the bobbin-casc and the rotation restraining device.

2. In a sewing machine, a reciprocating needle, a loop-taker, a take-up, a bobbincase having a loop-detaining horn, and a needle-loop tensioning spring coacting with said horn to tension the needle-loop imme diately prior to releasing the same.

3. In a sewing machine, a reciprocating needle,'a loop-taker, a throat-plate, a bobbin-case, means for restraining the bobbincase against` rotaticn7 and yielding means disposed below the throat-plate and adapted to nip the needle-loop after it has passed the rotation restraining means.

4. In a sewing machine, a reciprocating needle, a rotary hook, a bobbin-case, a bobbin-case support, a bobbin-case lifter, and a buffer spring adapted to cushion the movement of the bobbin-case initiated by said lifter.

5 In a sewing machine, a reciprocating needle, a rotary hook, a bobbin-case, a rotation restraining device, said case and device having loosely interengaging portions affording therebetween a passageway for the needle-loop. and a spring mounted independently of and bearing upon said bobbincase and yieldingly urging the latter at all times in a direction to open the entrance to such passageway.

6. In a sewing machine, a reciprocating needle, a rotary hook, a bobbin-case, a rotation restraining device, said case and device having loosely interengaging portions affording therebetween a passageway for the needle-loop, and a spring mounted inde pendently of and bearing upon'said bobbincase and yieldingly urging the latter at all times in a direction to open an entrance to such passageway 'at the side of said interengaging portions first passed by the rotary hook.

In testimony whereof I have signed my name to this specification.

MARTIN HEMLEB. 

